Wireless device and wireless communication method

ABSTRACT

According to one embodiment, a wireless device includes a receiver configured to receive a first beacon signal via a first channel; and control circuitry. The control circuitry is configured to: analyze the first beacon signal to obtain channel information for specifying a second channel, change an operation channel of the receiver from the first channel to the second channel, and change, in a case of not receiving a second beacon signal via the second channel during a predetermined period of time, the operation channel of the receiver from the second channel to the first channel. The receiver is further configured to receive a third beacon signal via the first channel after the operation channel is changed from the second channel to the first channel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/859,148, filed Dec. 29, 2017, which is a continuation of U.S.application Ser. No. 15/176,664, filed Jun. 8, 2016 (now U.S. Pat. No.9,887,732, issued Feb. 6, 2018), which in turn is a Continuation ofInternational Application No. PCT/JP2014/082538, filed on Dec. 9, 2014,and claims priority to Japanese Patent Application 2013-254858, filed inthe Japanese Patent Office on Dec. 10, 2013, the entire contents of eachof which are hereby incorporated by reference.

FIELD

Embodiments described herein relate to a wireless device and a wirelesscommunication method.

BACKGROUND

In a wireless communication, there is a problem that interference occurswith other systems or other appliances. Especially, in 2.4 GHz band,which is used in a wireless LAN or Bluetooth (trademark) etc., a problemis easily possible to occur that the band is simultaneously employedamong a plurality of systems or among a plurality of access points inthe same system. Accordingly, measure to avoid interference among thesystems or the access points is required.

Generally, as a method to avoid the interference, a channel hoppingscheme is employed which changes a channel according to a hoppingpattern of predetermined channels to perform communication. In theIEEE802. 15. 4, a method is standardized in which a node searches a newchannel by iteratively the following processes: specifying a candidatechannel from channels included in a hopping pattern, and performingchannel change to the candidate channel and channel scan. In the method,however, it is required to scan some channels even if a number ofcandidate channels to be scanned is restricted. Therefore, it takes timeto perform the channel change and the channel scan while powerconsumption increases.

On the other hand, in a communication system in which a child appliancefunctions as a relay node, the following method is proposed.Specifically, a parent appliance which uses a channel #f1 notifieschannel numbers (i.e., channel Nos.) of the previous channel #f0 and achange candidate channel #f2 to the child appliance. The child appliancewhich is notified of the channel numbers uses the previous channel #f0to notify the channel numbers of the current communication channel #f1and the change candidate channel #f2 to other child appliance(s) whichdirectly does not communicate with the parent appliance. In the method,the time taken for the channel change is shortened although the otherchild appliance only follows up one channel before the channel change.Therefore, in a case where there is a child appliance which is sleepingfor a long time, the child appliance is likely to not be able to followup a latest channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing one example of a wireless network systemaccording to a first embodiment.

FIG. 2 is a drawing for explaining an access scheme used at a time of achannel change in a system according to the first embodiment.

FIG. 3 is a drawing for explaining an access scheme used at a time of achannel change in a sleep node.

FIG. 4 is a block diagram of a wireless communication device which is ahub according to the first embodiment.

FIG. 5 is a block diagram of a wireless communication device which is anode according to the first embodiment.

FIG. 6 is a flow chart of channel management processing in a hub.

FIG. 7 is a flow chart of channel management processing in a node.

FIG. 8 is a drawing for explaining an access scheme used at a time of achannel change in a system according to a second embodiment.

FIG. 9 is a flow chart of channel management processing in a hubaccording to the second embodiment.

FIG. 10 is a drawing for explaining an access scheme used at a time of achannel change in a system according to a third embodiment.

FIG. 11 is a block diagram of a wireless communication device which is ahub according to a fourth embodiment.

FIG. 12 is a block diagram of a wireless communication device which is anode according to a fourth embodiment.

FIG. 13 is a block diagram of a wireless communication device which is ahub according to a fifth embodiment.

FIG. 14 is a block diagram of a wireless communication device which is anode according to a fifth embodiment.

FIG. 15 is a block diagram of a wireless communication device which is ahub according to a sixth embodiment.

FIG. 16 is a block diagram of a wireless communication device which is anode according to a sixth embodiment.

FIG. 17 is a hardware block diagram of a wireless communication deviceaccording to a seventh embodiment.

FIG. 18 is a perspective view of a wireless communication terminalaccording to an eighth embodiment.

FIG. 19 is a view showing a memory card according to an eighthembodiment.

FIG. 20 is a view showing a wireless communication system according to asixteenth embodiment.

FIG. 21 is a hardware block diagram of a node according to a sixteenthembodiment.

FIG. 22 is a hardware block diagram of a hub according to a sixteenthembodiment.

DETAILED DESCRIPTION

According to one embodiment, a wireless device includes a receiverconfigured to receive a first beacon signal via a first channel; andcontrol circuitry. The control circuitry is configured to: analyze thefirst beacon signal to obtain channel information for specifying asecond channel, change an operation channel of the receiver from thefirst channel to the second channel, and change, in a case of notreceiving a second beacon signal via the second channel during apredetermined period of time, the operation channel of the receiver fromthe second channel to the first channel. The receiver is furtherconfigured to receive a third beacon signal via the first channel afterthe operation channel is changed from the second channel to the firstchannel.

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

First Embodiment

FIG. 1 illustrates one example of a wireless network system relating toa first embodiment. A wireless network system 100 illustrated in FIG. 1includes a hub 10 and a plurality of nodes 20, 21 and 22. The hub 10includes a wireless communication device (or wireless device) that isoperated as a center device. Each node includes a wireless communicationdevice that is operated as a terminal of the center device. The hub 10is a communication target device for the nodes 20, 21 and 22, and thenodes 20, 21 and 22 are communication targets devices for the hub 10.

Each node incorporates one or more sensors for example, and wirelesslytransmits sensing information acquired by the sensor to the hub 10.Also, each node wirelessly receives control information or the likeneeded for communication from the hub.

The system may be a network called a body area network which is awireless network formed on a human body. In the body area network, thehub as a center device and the nodes as terminal devices are mounted ona human body, and communication between the hub and the nodes isperformed. As the sensors on mounted on the nodes, a biosensor such as asleep sensor, an acceleration sensor, an electrocardiogram sensor, abody temperature sensor and a pulse sensor is assumed. The presentembodiment is not limited to the body area network. The communicationnetwork system according to the present embodiment may be an arbitrarynetwork as long as a hub and nodes can be arranged and the hub operatesas the center device.

In the system, two types of channels are employed to communicate betweenthe hub and the nodes: a control channel and a data channel. For thecontrol channel, at least one channel is provided. In a case where aplurality of hubs are present, a plurality of control channels may beprovided. In the case, adjacent hubs may be allowed to employ the samecontrol channel. For the data channel, a plurality of channels areprovided. The hub can change the data channel to be used.

The hub periodically transmits a beacon signal which is an announcementsignal via the control channel (control channel beacon signal). The hubperiodically transmits a beacon signal which is an announcement signalvia the data channel (data channel beacon signal).

The period of the beacon signal transmitted via the control channel maybe the same as or different from the period of the beacon signaltransmitted via the data channel. An interval between successive twobeacon signals is called a beacon interval. Especially, an intervalbetween successive data channel beacon signals is called a data channelbeacon interval. In the data channel beacon interval, one or a pluralityof access periods are included. For example, one specific access periodmay be arranged or a plurality of access periods having respectivedifferent types may be arranged in a certain sequence. For example, asthe one specific access period, only an allocation-based access periodmay be arranged. Alternatively, as the plurality of access periodshaving respective different types, the allocation-based access periodand a contention-based access period may be arranged. Or, theallocation-based access period, the contention-based access period andan inactive period in which no communication are carried out may bearranged. In the case where the plurality of access periods havingrespective different types are arranged, a sequence of the periods to bearranged may not be limited to a specific sequence.

The allocation-based access period includes a plurality of slots. Eachnode can be allocated one or plural slots. Each node is not necessarilyallocated the slot in every beacon interval and may be allocated theslot every a given number of beacon intervals. In a case that the nodehas a frame for transmitting to the hub (a data frame, a control frame,a management frame, etc.), the node can transmit the frame in a slotallocated to node-self (node-self allocated slot).

The contention-based access period is a period in which communication iscarried out according to any contention-based access scheme. As thecontention-based access scheme, a slot Aloha-based scheme (slotted alohascheme) or the CSMA-based scheme can be employed. For example, in theslot Aloha-based scheme, a plurality of slots are arranged in thecontention-based access period, and in a case where the node has theframe for transmission, the node determines whether or not to transmitthe frame at a predetermined probability by generating a random number.When transmitting of the frame is determined, the node transmits theframe at a start timing of the slot. When no transmitting of the frameis determined, the transmission of the frame is skipped. A value of thepredetermined probability can be changed as a parameter. In a case thata plurality of nodes simultaneously transmits the frames at the starttiming of the slot, the signals of the frames collides with each otherand the transmission by the nodes may fail at a high probability. Inorder to use the slot in the contention-based access period, unlike theallocation-based access period, each node is not required to bepreviously allocated the slot by the hub.

In the control channel, a communication scheme employingcarrier-sensing, specifically, a CSMA (Carrier Sense MultipleAccess)-based communication scheme is assumed. In the CSMA scheme, thecarrier-sensing is carried out, and if a result of the carrier-sensingindicates an idle state, a transmission right can be acquired. During atime for which the hub transmits the beacon signal via the controlchannel, only the hub can occupy the time and the nodes cannotcommunicate during the time. The communication scheme used in thecontrol channel is not restricted to the CSMA-based communicationscheme. In the control channel, communication may be carried out in aslot unit or carried out at any timing but not in the slot-base.

Before the node connects to the hub, it awaits to receive the controlchannel beacon signal at the control channel. When the node receives thecontrol channel beacon signal, it performs channel change to the datachannel according to a data channel number (data channel No.) includedin the beacon signal. The node receives the data channel beacon signalat the data channel. The node performs, for example, connection processwith the hub and data transmission/reception with the hub by using thedata channel in the contention-based access period.

With reference to FIG. 2, the access scheme used at the time of channelchange in the system according to the first embodiment is explained. InFIG. 2(A), signals which the hub transmits/receives to/from the node inthe data channel are shown and in FIG. 2(B), signals which the hubtransmits/receives (here only transmission) to to/from the node in thecontrol channel are shown. A horizontal axis indicates a time axis and aright direction thereof along the drawing is a direction of timepassage. In the drawing, vertically long rectangles with character “B”indicate the beacon signals which the hub transmits. The vertically longrectangle with character “D” indicates a data frame which the hubreceives from the node, and the vertically long rectangle with character“A” indicates a response frame (Ack frame) which the hub transmits tothe node. In the present example, the case is shown that theallocation-based access period and the contention-based access periodare arranged in the data channel beacon interval although the presentembodiment does not be limited to the arrangement as stated above.

The hub first uses the data channel (Dch) of the channel #N₂ and thecontrol channel (Cch) of the channel #N₁. The hub determines to changethe data channel under any judgment. In this example, the hub determinesto change the data channel from the channel #N₂ to the channel #N₃. Thehub transmits the beacon signal 201 via the data channel of the currentused channel #N₂, the beacon signal including information showing thatthe data channel is to be changed and information on the data channelNo. after the change (new data channel No.). For example, a “datachannel change bit” is set to “1” (which means data channel changeexistence) and “data channel No.” field is set to the new data channelNo. “#N₃”. The hub employs the channel of the channel #N₃ on or aftertransmission of a next beacon signal 202. In the beacon signal 202,“data channel change bit” is set to “0”.

In the control channel beacon signal which the hub transmits, a “datachannel No.” field is included. The hub updates the “data channel No.”field to the channel #N₃. For example, the hub updates the data channelNo. in the beacon signal transmitted via the control channel to the“#N₃” on a trigger that data update (the channel change bit and the newchannel No. are set) is carried out in the data channel beacon signal inorder to change the data channel.

After the node connects to the hub, it performs control by usingsubstantially only the data channel. The node receives the beacon signal201 of the data channel and confirms the information of the data channelchange existence to recognize that the data channel is to be changed.The node changes the data channel to the channel of the new data channelNo. included in the beacon signal 201. In this example, the node changesthe data channel from the channel #N₂ to #N₃. The timing of changing thedata channel may be any timing. In the present embodiment, the timing ofchanging the data channel may be a timing at which the data channelbeacon signal 202 is transmitted from the hub subsequent to the datachannel beacon signal 201 which notifies the data channel change.

In this example, the “data channel change bit” field is provided in thedata channel beacon signal transmitted by the hub and existence ornon-existence of change of the data channel No. can be determined by avalue of one bit in the field. Therefore, processing load on the nodeborn when judging the existence or non-existence of change of the datachannel can be reduced. The field is not indispensable and theconfiguration not including the “data channel change bit” field can beadopted. In this case, the node always checks the “data channel No.”field and if the value of the field changes, it can determine for thedata channel to be required to be changed.

With reference to FIG. 3, the access scheme used at the time of thechannel change in the sleep node is explained.

FIG. 3(A) and FIG. 3(B) are substantially the same as the FIG. 2(A) andFIG. 2(B). However, in the data channel beacon interval, the inactiveperiod is arranged in addition to the allocation-based access period andthe contention-based access period. The additional arrangement of theinactive period does not influence the operation of the hub andtherefore more explanation is omitted. The arrangement is merely oneexample, and the present embodiment is not limited to the arrangement asstated above.

FIG. 3(C) illustrates an operation example of the data channel change inthe sleep node. The sleep node is a node which in order to reduce powerconsumption, periodically starts up (or is activated) and a constanttime after the starting up, again sleeps for a certain period of time.The sleep means a state in which the power consumption is lower thanpower consumption at a normal operation. As one example of the sleep, itmay be realized by stopping electric power supply to a part ofconstitution elements in the communication device or a part circuit inthe part. Alternatively, it may be realized by lowering an operatingfrequency or setting it to a state in which information cannot bereceived from a network. The sleep node having a long time of sleepingmay be called a long sleep node. The sleep node does not receive thedata channel beacon signal during the sleep period. The dashed rectangle211 with character “B” indicates to not receive the data channel beaconsignal. The sleep node enters into the sleep operation when it uses thedata channel of channel #N₂.

The node starts up at the time T1 during the sleep operation (A1). Afterthe sleep node starts up, it awaits reception of the beacon signal fromthe hub at the data channel during at least one data channel beaconinterval (A2). The node awaits the reception of the beacon signal at thedata channel of the No. (i.e., #N₂) used immediately before it entersinto the sleep operation. When the node receives the data channel beaconsignal which notifies the data channel change during that time, the nodechanges the data channel to the channel of the number included in thebeacon signal as be the case in FIG. 2.

When the sleep node does not receive data channel beacon signal from itsconnected hub during the at least one data channel beacon interval, thenode changes the operation channel to the control channel (#N₁) once.The sleep node then awaits reception of the control channel beaconsignal 212 transmitted from the connected hub at the control channel(A3). When the sleep node receives the control channel beacon signal212, it recognizes data channel No. currently used by the hub based onthe beacon signal. In this example, the node recognizes that the datachannel No. is #N₃. Accordingly, the node again changes the operationchannel from the control channel (#N₁) to the new data channel (#N₃).The node awaits the beacon signal 213 at the data channel (#N₃) afterthe change (A4).

FIG. 4 shows a configuration example of the hub including the wirelesscommunication device (or wireless device) according to the presentembodiment. The wireless communication device includes an antenna 10, aPHY&RF unit 20, a MAC unit 30 that is a communication processing deviceor control circuitry according to the present embodiment, and an upperlayer processor 40. The PHY&RF unit 20 includes a transmitter 21 and areceiver 22. The MAC unit 30 includes a transmission processor 31, areception processor 32, an access controller 33, and a channelcontroller 34.

The access controller 33 manages accesses by the control channel and thedata channel. The access controller 33 controls to transmit the beaconsignal at each channel at a desired timing. The access controller 33instructs to transmit the beacon signal of the control channel or thedata channel to the transmission processor 31. Upon receiving theinstruction, the transmission processor 31 generates a frame of thebeacon signal of the control channel or the data channel. Thetransmission processor 31 outputs the generated frame to the transmitter21. The beacon signal of the control channel includes channelinformation of the data channel (e.g., channel No.).

The transmitter 21 performs transmission by the control channel andtransmission by the data channel. The receiver 22 performs reception bythe control channel and reception by the data channel. The transmitter21 performs each transmission via each channel of No. instructed fromthe channel controller 34 which is described later. The receiver 22performs each reception via each channel of No. instructed from thechannel controller 34. The transmitter 20 may simultaneously orindependently perform the transmission by the data channel and thetransmission by the control channel, and the receiver 22 maysimultaneously or independently perform the reception by the datachannel and the reception by the control channel. The beacon signalframe of the control channel is transmitted via the control channel andthe beacon signal frame of the data channel is transmitted via the datachannel. A data frame is transmitted via the data channel.

The transmitter 21 performs processing of a physical layer on the frameinput from the transmission processor 31, according to a communicationscheme applied for the control channel or the data channel. Thetransmitter 21 performs D/A conversion and frequency conversion, etc. onthe frame subjected to the processing of the physical layer to generatea transmission signal. The transmitter 21 radiates the transmissionsignal as a radio wave into a space through the antenna 10. The numberof antenna(s) is one or plural number.

The receiver 22 receives a signal through the antenna 10. The receiver22 performs reception processing on the received signal, and output theframe obtained by the reception processing to the reception processor32. The reception processing may include processing of the physicallayer such as a frequency conversion to a baseband, and A/D conversion,analysis of a physical header of the frame subjected to the A/Dconversion and demodulation processing.

The channel controller 34 controls the setting of the PHY&RF unit 20,i.e., the setting of the transmitter 21 and the receiver 22. Forexample, the channel controller 34 sends, according to the instructionfrom the access controller 33, the number (i.e., channel No.) of thechannel to be used to the PHY&RF unit 20. The PHY&RF unit 20 sets,according to the channel No. notified from the channel controller 34,the operation channel of the transmitter 21 and the receiver 22. Twosets of the transmitter and the receiver may be provided for the datachannel and the control channel, respectively. In this example, thechannel controller 34 is provided independently from the accesscontroller 33 although the function of the channel controller 34 may beincorporated into the access controller 33 resulting in a processingunit of one block.

The reception processor 32 performs analysis or the like of a MAC headerof the frame input from the receiver 22. When the reception processor 32receives the connection request frame from the node, the receptionprocessor 32 notifies the connection request received from the node tothe access controller 33. The access controller 33 determines allocationof the slot(s) based on the connection request and notifies a result ofthe determination to the transmission processor 31. The accesscontroller 33 determines, for example, a number of slots to be allocatedwithin the data channel beacon interval, positions of the slotsallocated, a period of a beacon interval at which the slot(s) areallocated. The node transmits the connection request frame, for example,in the contention-based access period of the data channel.

The transmission processor 31 generates the connection response frameaccording to the result of the determination notified from the accesscontroller 33. In the case that the connection request frame notifiedfrom the node includes information on a sensor type of a sensor mountedin the node or information similar to the sensor type, the accesscontroller 33 may extract the information and notify the information tothe upper layer processor 40. The upper layer processor 40 may determinethe number of slots to be allocated within the beacon interval and theperiod of the beacon interval at which the slot(s) are allocated, etc.based on the notified information. In this case, the upper layerprocessor 40 notifies the information such as the number of slots to beallocated as determined to the access controller 33. The accesscontroller 33 performs slot allocation based on the notifiedinformation. Alternatively, if, in the side of the node which is thetransmission side of the connection request frame, information such asthe number of slots to be allocated and a period of a beacon interval atwhich the slots are allocated may be determined according to theprocessing as stated above and the determined value may be included inthe connection request frame. In this case, the upper layer processor 40may determine the number of slots to be allocated etc. based on thevalue included in the connection request frame. The access controller 33instructs the transmission processor 31 to generate the connectionresponse frame including allocation information of slots. Thetransmission processor 31 generates the connection response frame andtransmits it via the transmitter 21 through the data channel.

When the reception processor 32 determines that the frame input from thereceiver 22 is a data frame according to the analysis of the MAC headerof the frame, the recession processor 32 outputs the frame to the upperlayer processor 40 as necessary.

The access controller 33 receives notification such as a channel state(S/N ratio etc.) or an error state of frames transmitted/received forthe node, from the reception processor 32, and determined whether toperform the channel change.

When there is downlink data to be transmitted to the node, the upperlayer processor 40 passes a data frame including the data to thetransmission processor 31. The access controller 33 instructs thetransmission processor 31 to transmit the data frame to the node in adownlink slot acquired by any method (for example, method using a beaconsignal of the data channel or the control channel). The transmissionprocessor 31 performs a MAC header addition process or the like on theframe and outputs the processed frame to the transmitter 21. Thetransmitter 21 transmits the frame input from the transmission processor31 through the data channel. Specifically, the transmission processor 31performs the physical layer processing, such as modulation processingand physical header addition, to the frame. The transmission processor31 performs D/A conversion or frequency conversion to the processedframe and radiates the signal as a radio wave to the space through theantenna 10.

FIG. 6 is a flow chart of channel management processing performed by thehub.

The access controller 33 of the hub starts the processing at any triggersuch as periodically or when any condition is satisfied. The accesscontroller 33 first determines whether to perform the channel change ofthe data channel (S11). For example, it determines whether to performthe channel change based on information such as the channel state or theerror state of the frames transmitted/received for the node, notifiedfrom the reception processor 32. When the access controller 33determines not to change the data channel (NO in S12), it ends theprocessing.

When the access controller 33 determines to change the data channel (YESin S12), it instructs the transmission processor 31 to generate a beaconsignal frame in which the channel change existence information being thebit set in the data channel change field and the new data channel No.are inserted (S13). The transmission processor 31 generates the beaconsignal frame of the data channel according to the instruction from theaccess controller 33.

The access controller 33 instructs the transmission processor 31 tochange the data channel No. included in the control channel beaconsignal to the new data channel No. (S14). The transmission processor 31generates the beacon signal frame, of the control channel, including thenew data channel No. according to the instruction from the accesscontroller 33.

The access controller 33 instructs the transmission processor 31 totransmit the beacon signal frame at a beacon transmission timing of thedata channel, the beacon signal frame including the channel changeexistence information and the new data channel No. The transmissionprocessor 31 transmits the beacon signal frame at a beacon transmissiontiming of the data channel via the transmitter 20 by the data channel,the beacon signal frame including the channel change existenceinformation and the new data channel No. (S15).

The access controller 33 instructs the transmission processor 31 totransmit the beacon signal frame including the new data channel No. at abeacon transmission timing of the control channel. The transmissionprocessor 31 transmits the beacon signal frame including the new datachannel No. at a beacon transmission timing of the control channel viathe transmitter 20 by the control channel (S15).

The access controller 33 then changes the setting of the transmitter 20and the receiver 22 via the channel controller 34 so that the channel ofthe new data channel No. is used on or subsequent to transmission of thenext data channel beacon signal.

FIG. 5 illustrates a block diagram of an example of configuration of thenode including the wireless communication device (or wireless device)according to the present embodiment. The node includes an antenna 110, aPHY&RF unit 120, a MAC unit 130 that is a communication processingdevice or control circuitry according to the present embodiment, and anupper layer processor 140. The PHY&RF unit 120 includes a transmitter121 and a receiver 122. The MAC unit 130 includes a transmissionprocessor 131, a reception processor 132, an access controller 133 and achannel controller 134. The transmission processor 131 and receptionprocessor 132 may include a transmission buffer and a reception buffer,respectively. The upper layer processor 140 includes a sensorinformation acquirer which acquires the information of the sensor. Theinformation of the sensor includes not only sensing information of thesensor but also information for specifying a state of the sensor andinformation on a sensing time etc.

The upper layer processor 140 outputs a transmission request forconnection with the hub to the access controller 133 at predeterminedtiming, such as at the start or at the generation of transmission data.The upper layer processor 140 generates a frame including transmissiondata, such as sensing information, and outputs the frame to thetransmission processor 131. Examples of the transmission data includesensing information acquired by a sensor such as a biological sensor,data indicating a result of processing of the sensing information by anapplication or the like, and data including a current state of the node.However, the transmission data is not limited to specific data.

The upper layer processor 140 may be configured by a program executed bya processor such as CPU, may be configured by hardware, or may beconfigured both of software and hardware. The upper layer processor 140may perform processing of communication protocol of an upper layerhigher than MAC layer, such as TCP/IP or UDP/IP.

When the access controller 133 receives the transmission request fromthe upper layer processor 140, the access controller 133 outputs atransmission instruction of the connection request frame to thetransmission processor 131. The transmission processor 131 outputs theconnection request frame to the transmitter 121 upon receiving atransmission instruction from the access controller 133.

The transmitter 121 performs transmission by the control channel andtransmission by the data channel. The receiver 122 performs reception bythe control channel and reception by the data channel. The transmitter121 transmits the frame via the channel of No. instructed from thechannel controller 134 which is described later. Specifically, thetransmitter 121 performs processing of a physical layer on the frameinput from the transmission processor 131. The transmitter 121 performsD/A conversion and frequency conversion, etc. on the frame subjected tothe processing of the physical layer to generate a transmission signal.The transmitter 121 radiates the transmission signal as a radio waveinto a space through the antenna 110.

The receiver 122 receives the frame via the channel of No. instructedfrom the channel controller 134. For example, the receiver 122 receivesthe beacon signal frame transmitted via the control channel by the hub.The receiver 122 receives the beacon signal frame transmitted via thedata channel by the hub. Specifically, the receiver 122 receives asignal through the antenna 110 and performs reception processing on thereceived signal to obtain a reception frame. The receiver 122 outputsthe reception frame to the reception processor 132. The receptionprocessing may include processing of the physical layer such as afrequency conversion to a baseband, and A/D conversion, analysis of aphysical header of the frame subjected to the A/D conversion anddemodulation processing.

The channel controller 134 controls the setting of the PHY&RF unit 120,i.e., the setting of the transmitter 121 and the receiver 122. Forexample, the channel controller 134 sends the number (i.e., channel No.)of the channel to be used to the PHY&RF unit 120. The PHY&RF unit 20sets the transmitter 21 and the receiver 22 so that the transmitter 21and the receiver 22 perform transmission/reception at the channel of No.notified from the channel controller 134. In this example, the channelcontroller 134 is provided independently from the access controller 133although the function of the channel controller 134 may be incorporatedinto the access controller 133 resulting in a processing unit of oneblock.

Two antennas may be arranged in the node and two sets of the transmitterand the receiver may be provided for the data channel and the controlchannel, respectively. In this configuration, the control channel andthe data channel may be simultaneously employed.

The reception processor 132 performs analysis or the like of a MACheader of the frame input from the receiver 122. When the received frameis a connection response frame, the reception processor 132 notifies theconnection response to the access controller 133. When the accesscontroller 133 receives the connection response frame, it determines tochange the operation channel of the transmitter 121 and the receiver 122from the control channel to the data channel. The access controller 133instructs the channel controller 134 to perform the channel change fromthe control channel to the data channel. Upon receiving the instruction,the channel controller 134 instructs the PHY&RF unit 120 to change theoperation channel to the data channel.

The access controller 133 controls access of the data channel based oninformation such as allocation slot information of the data channelincluded in the connection response frame. The access controller 133knows a buffering state of frames in the transmission processor 131. Theaccess controller 133 instructs the transmission processor 131 totransmit the data frame at the timing of the slot allocated to thenode-self in the allocation-based access period. The transmissionprocessor 131 performs a MAC header addition process or the like on thedata frame and outputs the processed frame to the transmitter 121.

When the access controller 133 transmits the frame such as the dataframe in the contention-based access period, it determines, in the caseof slotted-aloha scheme, transmission or non-transmission at apredetermined transmission probability at a start timing of any slot.When the transmission is determined, the access controller 133 instructsthe transmission processor 31 to transmit the frame at the start timingof the slot. When the non-transmission is determined, the accesscontroller 133 skips the transmission and performs similar processing ata subsequent slot(s) in the contention-based access period.

In the CSMA-based scheme, the access controller 133 performscarrier-sensing via the reception processor 132 by using the receiver122. If the carrier is not detected, i.e., a signal having a higherlevel than a predetermined level is not received, the access controller133 determines that the result of the carrier-sensing indicates an idlestate. In this case, the node acquires a transmission right and controlsthe transmission processor 31 to transmit the frame. Even in theCSMA-based scheme, access may be carried out in a slot unit as the caseof the slotted aloha access. In this case, for example, thecarrier-sensing is carried out at a start timing of the slot, and if theresult of the carrier-sensing indicates the idle state, the transmissionright is acquired to transmit the frame at the slot.

In FIG. 5, signals are sent/received among the carrier-sensing relatedblocks via the reception processor 132 although the receiver 122 andaccess controller 133 directly send/receives the signals to/from eachother.

When the reception processor 132 determines, as a result of analysis onthe MAC header of the frame input from the receiver 122 or the like,that the received frame is a data frame, the reception processor 132outputs the frame after the processing to the upper layer processor 140as necessary.

The channel controller 134 and the access controller 133 may internallyhold information necessary for various controls or may hold theinformation in an accessible storage not shown. For example, the statusof the node, and the status of the hub, channel No. of the data channel,channel No. of the control channel or the like may be held. Examples ofthe status of the node include information indicating whether theconnection processing is already executed and information of theremaining amount of battery. The status of the hub may include theinformation of the transmission timing of the beacon signal of thecontrol channel or the transmission timing of the beacon signal of thedata channel. Further, the status of the hub may include ON/OFF state(i.e., Enable/Disable state) of the power of the hub or otherinformation.

Below, the operation example in the node is described. The accesscontroller 133 manages an access by the control channel based on atransmission request from the upper layer processor 140. The node maypreviously store therein information for identifying the control channelor perform channel search to specify the control channel.

The access controller 133 receives the beacon signal transmitted fromthe hub by the control channel and acquires information required togenerate the connection request and information of the data channel. Theaccess controller 133 instructs the transmission processor 131 totransmit the connection request frame based on the acquired information.The transmission processor 131 generates the connection request frameand transmits it via the transmitter 121 thought the control channel.The access controller 133 awaits the connection response frame from thehub.

The access controller 133, upon receiving the connection response frame,instructs the channel controller 134 to change the operation channelfrom the control channel to the data channel. The channel controller 134notifies, according to the instruction, information on the data channelto the PHY&RF unit 120. The PHY&RF unit 120 changes, according to thenotification from the channel controller 134, the operation channel tothe data channel.

The access controller 133 manages an access of the data channel based onallocation slot information of the data channel included in theconnection response frame. The access controller 133 knows a bufferingstate of frames in the transmission processor 131. The access controller133 instructs the transmission processor 131 to transmit the data frameat the timing of the slot allocated to the node-self. Alternatively, theaccess controller 133 acquires the transmission right according to thecontention-based access scheme used in the contention-based accessperiod and then instructs the transmission processor 31 to transmit thedata frame.

Subsequently, as the operation of the node, the operation at the channelchange is described.

FIG. 7 is a flow chart of the channel management processing in the node.The access controller 133 of the node awaits reception of the beaconsignal from the hub at the data channel of the channel No. set to thenode-self during the beacon interval of the data channel or more (S101,S102). When the access controller 133 receives the data channel beaconsignal from the hub during awaiting the beacon signal (YES in S101), itdetermines based on the beacon signal whether the data channel ischanged (S103). For example, when the beacon signal includes the channelchange existence information, the access controller 133 determines thatthe data channel is changed. When the data channel is not changed, theprocessing returns to step S101, the access controller 133 awaits thereception of the data channel beacon signal from the hub.

When the access controller 133 determines that the data channel ischanged (YES in S103), it controls the channel controller 134 to changethe data channel to the channel of the new data channel No. specified inthe data channel beacon signal (S104). Specifically, the accesscontroller 133 instructs the transmitter 121 and the receiver 122 toperform channel change to the new data channel No. via the channelcontroller 134. The timing of the channel change may be a transmissiontiming of the data channel beacon signal next transmitted or may be onthe instant if the node does not perform communication in the currentbeacon interval.

When the access controller 133 does not receives the data channel beaconsignal during the beacon interval of the data channel or more (NO inS101 and YES in S102), it changes the operation channel to the controlchannel (S105). Specifically, the access controller 133 instructs, viathe channel controller 134, the transmitter 121 and the receiver 122 toperform channel change to the control channel No.

The access controller 133 awaits reception of the control channel beaconsignal at the control channel (S106). When the access controller 133receives the control channel beacon signal (YES in S106), it recognizesthe new data channel No. based on the beacon signal. The accesscontroller 133 then change the operation channel from the controlchannel to the new data channel (S104). Specifically, the accesscontroller 133 instructs, via the channel controller 134, thetransmitter 121 and the receiver 122 to perform channel change to thenew data channel No.

According to the first embodiment, the hub stores at least the new datachannel No. among the channel change existence information and the newdata channel No. in the data channel beacon signal. The hub storesinformation on the new data channel No. in the control channel beaconsignal. Therefore, the normal node, which is not sleeping, can shift tothe new data channel without changing the operation channel to thecontrol channel. On the other hand, the sleep node returns from thesleep and then changes the operation channel to the control channel(i.e., a minimum number of times of channel changes) to know the datachannel and thereby can shift to the new data channel.

Second Embodiment

In the first embodiment, the method is proposed in which the channelchange and the new data channel No. are notified via the data channelbeacon signal. In the second embodiment, in addition to the channelchange and the new data channel No., the data channel change timing isnotified. In a part or all of data channel beacon signals transmittedbefore the change timing of the data channel, the channel changeexistence information, the new data channel No. and data channel changetiming are set. Therefore, in the case where there is a node whichperiodically starts up and sleeps during a period of time other thanthat, the started up node is highly likely to follow up the data channelwithout shifting to the control channel. Below, details thereof aredescribed.

Among nodes, the node may exist which sleeps during a period of timethan the transmission and reception timings of the node-self. Forexample, it is considered that the node exists which starts up everyseveral data channel beacon signals and then receives the data channelbeacon signal. In this case, if, as in first embodiment, the datachannel is changed at a transmission timing of a data channel beaconsignal transmitted next to the data channel beacon signal including thechannel change existence information and the new data channel No., thenode which receives the data channel beacon signal one time every theseveral beacon signal cannot follow the change of the data channel.Therefore, the node loses a data channel beacon signal transmitted viathe new data channel after the change.

In the case, in the first embodiment, the node changes the operationchannel to the control channel once and finds the new data channel toshift to the new data channel. However, this requires two times ofchannel changes before shifting to the new data channel, resulting inthat power consumption in the node increases.

In the second embodiment, in order to solve this problem, the datachannel change timing is added to data channel beacon signal as well asthe channel change existence information and the new data channel No.Below, the present embodiment is described in detail.

With reference to FIG. 8, an access scheme used at the time of thechannel change in the system according to the present embodiment isexplained.

The difference from FIG. 2 is that the hub inserts the data channelchange timing in the data channel beacon signal in addition to thechannel change and the new data channel No. In the example shown in FIG.2, information for identifying a transmission timing of the beaconsignal 301 is inserted as the data channel change timing. When theaccess controller 33 of the hub determines to change the data channel,it determines a change timing of the data channel and insertsinformation on the determined timing in the data channel beacon signaltogether with the channel change and the new data channel No.

The node which has received the data channel beacon signal recognizesthe new data channel No. and the timing for changing the data channel tothe new data channel. According the timing, the node changes the datachannel to the channel of the new data channel No. by controlling thePHY&RF unit 120. In the example shown in FIG. 8, on or aftertransmission of the beacon signal 301, the node employs the channel #N₃in the data channel by controlling the transmitter 121 and the receiver122 in the PHY&RF unit 120.

An example of determining the data channel change timing is describedblow. For example, it is assumed that from nodes connected to the hub,the hub previously receives information on a period (interval) ofstarting up and a sleep time length. The information indicates, forexample, that the node starts up every what number of beacon intervalsto receive the data channel and entries into the sleep again on or aftera next beacon transmission timing. The hub determines the data channelchange timing according to a longest period of starting up among thenodes connected to the hub. The period of starting up corresponds to areception period (reception interval) of the data channel beacon.

As one example, the hub determines the data channel change timing to atransmission timing of the beacon signal the longest period length aftertransmission of the data channel beacon signal which notifies thechannel change. However, among the nodes connected to the hub, a longsleep node which starts up in an excessively long period may exist. Thelong sleep node may be defined as a node which does not successivelyreceive the beacon signals X times. A value of X (upper bound) is notlimited to a specific value: however, X is 2 or more in order todistinguish the long sleep node from the normal sleep node. If the longsleep node exists among the nodes, the hub may determines the datachannel change timing according to one of periods of starting up in thenodes other than the long sleep node.

The format of information on the data channel change timing inserted inthe data channel beacon signal may be any format. For example, thechange timing may be specified by a sequence number (SN) of the datachannel beacon at the change timing of the channel. Alternatively, ifthe changing timing is a transmission timing of the beacon signal afterthe data channel beacon signal is transmitted x times, the change timingmay be specified by “x”.

FIG. 9 is a flow chart of channel management processing performed by thehub according to the present embodiment.

The access controller 33 of the hub starts the processing at any triggersuch as periodically or when any condition is satisfied. The accesscontroller 33 first determines whether to perform the channel change ofthe data channel (S201). When the access controller 33 determines not tochange the data channel (NO in S202), it ends the processing.

When the access controller 33 determines to change the data channel (YESin S202), it instructs the transmission processor 31 to generate abeacon signal frame which includes the channel change existenceinformation being the bit set in the data channel change field, the newdata channel No. and information on the data channel change timing(S203). The transmission processor 31 generates the beacon signal frameof the data channel according to the instruction from the accesscontroller 33.

The access controller 33 determines whether it becomes the change timingof the data channel (S204). When it becomes the data channel changetiming, the access controller 33 instructs the transmission processor 31to change the data channel No. included in the control channel beaconsignal to the new data channel No. (S205). The transmission processor 31generates the beacon signal frame, of the control channel, including thenew data channel No. according to the instruction from the accesscontroller 33. When it does not become the data channel change timing,the access controller 33 does not instruct the update of the number ofthe data channel to the transmission processor 31.

The access controller 33 instructs the transmission processor 31 totransmit the beacon signal frame at a beacon transmission timing of thedata channel, the beacon signal frame including the channel changeexistence information, the new data channel No. and the data channelchange timing (S206). The transmission processor 31 transmits the beaconsignal frame at a beacon transmission timing of the control channel viathe transmitter 20 by the control channel, the beacon signal frameincluding the new data channel No. (S206). The access controller 33changes the setting of the operation channel in the transmitter 20 andthe receiver 22 via the channel controller 34 so that the new datachannel is used for transmission/reception of the data channel beaconsignal and other signals on or after the change timing of the datachannel.

According to the second embodiment, the data channel change timing isdetermined in a case where the data channel is determined to be changed,and information such as the data channel change timing is included ineach data channel beacon signal transmitted before the data channelchange timing. Therefore, the node which periodically starts up andreceives the data channel beacon signal can recognize the data channelchange and the timing thereof without shifting to the control channel ata high likelihood, and follow up the data channel after the change.

Third Embodiment

In the first and the second embodiments, although the transmissionperiod of the control channel beacon signal is constant, in the thirdembodiment, a case is shown in which the transmission period of thecontrol channel beacon signal is changed when the data channel ischanged.

With reference to FIG. 10, an access scheme used at the time of thechannel change in the system according to the third embodiment isexplained.

The hub according to the present embodiment sets, for the purpose ofreduced power consumption, a transmission period of the control channelbeacon signal to a longer value than that of a base period. For example,the transmission period is set to a value twice as long as the baseperiod. The base period is predetermined such that the signal collisiondoes not occur among adjacent hubs. Specifically, a case may be in whichthe control channel beacon signal has functions of sharing states ofhubs and the hubs transmit respective control channel beacon signals atthe same control channel in a time sharing manner. Under such acircumstance, the base period of the control channel beacon signal ispredetermined such that the signal collision is prevented among theadjacent hubs.

When the hub determines the data channel change, the hub, at a triggerof the data channel change, shortens the transmission period of thecontrol channel beacon signal or sets it back to the base period. In acase where the hub sets the transmission period shorter than the baseperiod, the hubs previously confirm any periods available by the hubs inorder to prevent the signal collision among the adjacent hubs. In a casewhere there are a plurality of hubs, each hub receives the controlchannel beacon signals transmitted by other hubs than the node-self, andthereby can recognize information such as the data channel used by theadjacent other hubs. Therefore, the hub may determine to change the datachannel to the channel unused by the adjacent other hubs.

As shown in FIG. 10(A), the hub notifies the data channel change timingetc. by the data channel beacon signal 401 via the data channel#N₂. Inthis example, the data channel change timing is a transmission timing ofthe data channel beacon signal 402 which is transmitted next to the datachannel beacon signal 401. The data channel after the change is thechannel#N₃. In this case, as shown in FIG. 10(B), the hub shortens thetransmission period of the control channel beacon signal on or after thetransmission timing of the data channel beacon signal 401 (A31).Alternatively, the hub may shorten the transmission period of thecontrol channel beacon signal on or after a transmission timing of thebeacon signal transmitted next to the data channel beacon signal 401.

Although in this example, the channel is changed from the transmissiontiming of the beacon signal transmitted next to the data channel beaconsignal 401, the channel change may be made from the transmission timingof the beacon signal transmitted after transmission of several datachannel beacon signals from the data channel beacon signal 401. In thiscase, on or after the channel change timing or a beacon signaltransmission timing before the channel change timing by one beaconinterval or more, such control may be made that the transmission periodof the control channel beacon signal is shortened.

On the other hand, as shown in FIG. 10(C), the sleep node starts up at atime T2. After the sleep node starts up at the time T2, the sleep nodeawaits reception of the data channel beacon signal at the channel #N₂during one data channel beacon interval (A32).

However, the sleep node cannot receive the data channel beacon signal atthe channel#N₂. For this reason, the sleep node shifts to the controlchannel#N₁ and awaits reception of the beacon signal (A33).

In the example shown in the drawing, the sleep node receives a pluralityof control channel beacons 411 and 412 during awaiting the beaconsignal. Although in the example shown in FIG. 3(C) in the firstembodiment, the sleep node awaits reception of the beacon signal duringthe same time period as that in shown in FIG. 10(C), the number of timesof reception of the beacon signal is only one. In contrast, in theexample in FIG. 10(C), the number of times of reception of the beaconsignals is two since the transmission period of the beacon signal isshortened.

Therefore, if the node successfully receives the control channel beaconsignal 411 which is first transmitted (there is no frame error) andconfirm the new data channel No., the node may omit awaiting processingof the subsequent control channel beacon signal and reception processingthereof. Thereby, the node can rapidly shift to the new data channel.

Even if there is the frame error on the first received control channelbeacon signal 411, the node can early receive the second control channelbeacon signal and thus it becomes possible to early shift to the newdata channel at a high likelihood.

When the sleep node confirms the new data channel No., the sleep nodechanges the operation channel from the control channel to the datachannel (A34).

After the hub shortens the transmission period of the control channelbeacon signal, if the predetermined condition is satisfied, the hubagain lengthens the transmission period of the control channel beaconsignal. As the predetermined condition, it may include that the hub canconfirm that a constant number or a constant ratio of the nodesconnected to the hub have shifted to the new channel. The examplethereof is that all of the nodes connected to the hub have shifted tothe new channel.

Alternatively, as the predetermined condition, it may include that aconstant period of time lapses after a predetermined trigger occurs. Theexample thereof is that a constant period of time lapses after a timingat which the transmission period is shortened. Alternatively, instead ofthe timing at which the transmission period is shortened, it may be atiming at which the hub has confirm that a predetermined number of nodes(the value of which is smaller than the total number of the nodes) or apredetermined ratio (the value of which is smaller than one) of nodesshifted to the new channel.

As the method in which the hub confirms that the nodes connected to thehub shifted to the new channel, the following method is proposed.

As one example, the node which shifted to the new channel transmits, bythe data channel after the change, any data or a control signal such asa channel change notification (channel change announcement) at the slotallocated to the node-self. The any data may be data required totransmit to the hub (for example, ordinary data such as sensor data) ornull data having no frame body.

In the example of FIG. 10(A), the node transmits the channel changenotification or data at the slot allocated to the node-self within theallocation-based access period in the third data channel beacon intervalafter shifting to the new channel#N₃. The signal shown by the rectanglewith character “M” means this.

In the example of FIG. 10(C), the sleep node transmits the channelchange notification or data at the slot allocated to the node-selfwithin the allocation-based access period in the first data channelbeacon interval after shifting to the new channel#N₃. The signal shownby the rectangle with character “M” means this.

According to the third embodiment, at the time of data channel change,the transmission period of the control channel beacon signal isshortened. This enables the node to rapidly shift to the new channel ata high likelihood. Other than the case of the data channel change, thetransmission period of the control channel beacon signal is lengthenedand the power consumption of the hub can be reduced.

Fourth Embodiment

FIG. 11 shows a block diagram of a hub including a wirelesscommunication device according to a fourth embodiment.

In the hub shown in FIG. 11, buffers 71 and 72 are added to the MAC unit30 of the wireless communication device according to the firstembodiment shown in FIG. 4. The buffers 71 and 72 are connected to thetransmission processor 31 and the reception processor 32. The upperlayer processor 40 performs input and output with the transmissionprocessor 31 and the reception processor 32 through the buffers 71 and72. The buffers 71 and 72 can be, for example, arbitrary volatilememories or non-volatile memories. In this way, the buffers 71 and 72can be provided to hold the transmission frame and the reception framein the buffers 71 and 72. The retransmission process, QoS controlaccording to the frame type etc. or the output process to the upperlayer processor 40 can be easily performed.

The configuration of adding the buffers can be similarly applied to thenode.

FIG. 12 shows a block diagram of a node including a wirelesscommunication device according to a fourth embodiment.

In the node shown in FIG. 12, buffers 171 and 172 are added to the MACunit 130 of the wireless communication device according to the firstembodiment shown in FIG. 5. The buffers 171 and 172 are connected to thetransmission processor 131 and the reception processor 132,respectively. The upper layer processor 140 performs input and outputwith the transmission processor 131 and the reception processor 132through the buffers 171 and 172. The buffers 171 and 172 can be, forexample, arbitrary volatile memories or non-volatile memories. In thisway, the buffers 171 and 172 can be provided to hold the transmissiondata and the reception data in the buffers 171 and 172. Theretransmission process, QoS control according to the frame type etc., orthe output process to the upper layer processor 140 can be easilyperformed.

Fifth Embodiment

FIG. 13 shows a block diagram of a hub including a wirelesscommunication device according to a fifth embodiment.

The hub illustrated in FIG. 13 has a form that a bus 73 is connected tothe buffers 71 and 72 and the access controller 33 in the fourthembodiment illustrated in FIG. 11, and an upper layer interface 74 and aprocessor 75 are connected to the bus 73. The MAC unit 30 is connectedwith the upper layer processor 40 at the upper layer interface 74. Inthe processor 75, firmware is operated. By rewriting the firmware,functions of the wireless communication device can be easily changed.The function of at least one of the access controller 33 and the channelcontroller 34 may be achieved by the processor 75.

FIG. 14 shows a block diagram of a node including a wirelesscommunication device according to a fifth embodiment.

The node illustrated in FIG. 14 has a form that a bus 173 is connectedto the buffers 171 and 172 and the access controller 133 in the fourthembodiment illustrated in FIG. 12, and an upper layer interface 174 anda processor 175 are connected to the bus 173. The MAC unit 130 isconnected with the upper layer processor 140 at the upper layerinterface 174. In the processor 175, the firmware is operated. Byrewriting the firmware, functions of the wireless communication devicecan be easily changed. The function of at least one of the accesscontroller 133 and the channel controller 134 may be achieved by theprocessor 175.

Sixth Embodiment

FIG. 15 shows a block diagram of a hub including a wirelesscommunication device according to a sixth embodiment.

The wireless communication device illustrated in FIG. 15 has a form thata clock generator 76 is connected to the MAC unit 30 in the hub relatingto the first embodiment illustrated in FIG. 4. The clock generator 76 isconnected through an output terminal to an external host (the upperlayer processor 40 here), and a clock generated by the clock generator76 is given to the MAC unit 30 and is also outputted to the externalhost. By operating the host by the clock inputted from the clockgenerator 76, a host side and a wireless communication device side canbe operated in synchronism. In this example, the clock generator 76 isarranged on the outer side of the MAC unit 30, however, it may beprovided inside the MAC unit 30.

FIG. 16 shows a block diagram of a node including a wirelesscommunication device according to a sixth embodiment.

The wireless communication device illustrated in FIG. 16 has a form thata clock generator 176 is connected to the MAC unit 130 in the noderelating to the first embodiment illustrated in FIG. 5. The clockgenerator 176 is connected through an output terminal to an externalhost (the upper layer processor 140 here), and a clock generated by theclock generator 176 is given to the MAC unit 130 and is also outputtedto the external host. By operating the host by the clock inputted fromthe clock generator 176, the host side and the wireless communicationdevice side can be operated in synchronism. In this example, the clockgenerator 176 is arranged on the outer side of the MAC unit 130,however, it may be provided inside the MAC unit 130.

Seventh Embodiment

FIG. 17 illustrates an example of a hardware configuration of a wirelesscommunication device in accordance with a seventh embodiment. Thishardware configuration is only provided by way of example, and variousmodifications can be made to this hardware configuration. The operationof the wireless communication device illustrated in FIG. 17, detaileddescription of which is omitted, is performed in the same or similarmanner as in the wireless communication devices described in the contextof the previous embodiments, and the following explanation focuses onthe differences in respect of the hardware configuration. It should benoted that the illustrated hardware configuration can be applied both tothe wireless communication device that operates as a hub and to thewireless communication device that operates as a node.

This wireless communication device includes a baseband unit 211, an RFunit 221, and antennas 50(1) to 50(N) (where N is an integer equal orlarger than one).

The baseband unit 211 includes a control circuit 212, a transmissionprocessing circuit 213, a reception processing circuit 214, DAconversion circuits 215, 216, and AD conversion circuits 217, 218. TheRF unit 221 and the baseband unit 211 may be collectively configured asone-chip IC (integrated circuit) or may be configured as independentchips.

As one example, the baseband unit 211 is a baseband LSI or a basebandIC. Alternatively, the baseband unit 211 may include an IC 232 and an IC231 in the illustrated manner as indicated by dotted lines. In thiscontext, components may be incorporated in a distributed manner on theseICs such that the IC 232 includes the control circuit 212, thetransmission processing circuit 213, and the reception processingcircuit 214 while the IC 231 includes the DA conversion circuits 215,216 and the AD conversion circuits 217, 218.

The control circuit 212 is mainly configured to execute thefunctionality of the MAC processor 30 and 130 of FIGS. 4 and 5, etc. Thefunctionality of the upper layer processor 40 and 140 may be included inthe control circuit 112.

The transmission processing circuit 213 corresponds to the section thatperforms the processing before DA conversion processing in thetransmitter 21 and 121 in FIGS. 4 and 5, etc. Specifically, thetransmission processing circuit 213 mainly performs processingassociated with the physical layer including addition of a preamble anda PHY header, encoding, modulation (which may include MIMO modulation),and generates, for example, two types of digital baseband signals(hereinafter referred to as the digital I-signal and Q-signal). Itshould be noted that another configuration can be contemplated accordingto which the functionality performed before DA conversion processing inthe transmitter 21 and 121 of FIGS. 4 and 5, etc. may be included in thetransmission processing circuit 213, the functionality performed afterAD conversion processing in the receiver 22 and 122 may be included inthe reception processing circuit 214.

The communication processing device of this embodiment corresponds, forexample, to the control circuit 212, the transmission processing circuit213, and the reception processing circuit 214. The communicationprocessing device of this embodiment may take either configuration of aone-chip IC configuration or a multiple-chip IC configuration.

The DA conversion circuits 215 and 216 correspond to the sectionassociated with the digital-to-analog conversion in the transmitter 21and 121 of FIGS. 4 and 5, etc. The DA conversion circuits 215 and 216are configured to perform digital-to-analog conversion for the signalsinput from the transmission processing circuit 213. More specifically,the DA conversion circuit 215 converts a digital I-signal into an analogI-signal, and the DA conversion circuit 216 converts a digital Q-signalinto an analog Q-signal. It should be noted that there may be a casewhere the signals are transmitted as single-channel signals without thequadrature modulation being performed. In this case, it suffices thatone single DA conversion circuit is provided. In addition, whentransmission signals of one single channel or multiple channels aretransmitted in a distributed manner in accordance with the number ofantennas, DA conversion circuits may be provided in the numbercorresponding to the number of the antennas.

The RF unit 221, by way of example, is an RF analog IC or ahigh-frequency wave IC. The transmitting circuit 222 in the RF unit 221corresponds to the section associated with the processing following thedigital-to-analog conversion out of the functions of the transmitter 21and 121 illustrated in FIGS. 4 and 5, etc. The transmitting circuit 222includes a transmission filter that extracts a signal of a desiredbandwidth from the signal of the frame that has been subjected to thedigital-to-analog conversion by the DA conversion circuits 215 and 216,a mixer that performs up-conversion for the signal that has beensubjected to the filtering to the wireless frequency using a signalhaving a predetermined frequency supplied from an oscillation device, apre-amplifier (PA) that performs amplification for the signal that hasbeen subjected to the up-conversion, and the like.

The receiving circuit 223 in the RF unit 221 corresponds to the sectionassociated with the processing prior to the analog-to-digital conversionfrom among the functions of the receiver 22 and 122 illustrated in FIGS.4 and 5, etc. The receiving circuit 223 includes an LNA (low noiseamplifier) that amplifies the signal received by the antenna, a mixerthat performs down-conversion of the amplified signal to the basebandusing a signal having a predetermined frequency supplied from anoscillation device, a reception filter that extracts a signal of adesired bandwidth from the signal that has been subjected to thedown-conversion, and the like. More specifically, the receiving circuit223 performs quadrature demodulation for the reception signal, which hasbeen subjected to the low noise amplification by a low noise amplifier,by carrier waves with 90 degree phase shift with respect to each otherand thus generates an I-signal (In-phase signal) having the same phaseas that of the reception signal and a Q-signal (Quad-phase signal) whosephase is delayed by 90 degrees with respect to the reception signal. TheI-signal and the Q-signal are output from receiving circuit 223 afterbeing subjected to the gain adjustment.

The control circuit 212 may control the operation of the transmissionfilter of the transmitting circuit 222 and the reception filter of thereceiving circuit 223. Another controller that controls the transmittingcircuit 222 and the receiving circuit 223 may be provided and the sameor similar control may be realized by the control circuit 212 sendinginstructions to that controller.

The AD conversion circuits 217, 218 in the baseband unit 211 correspondto the section of the receiver 22 and 122 that performs theanalog-to-digital conversion out of the processing of the receiver 22and 122 as illustrated in FIGS. 4 and 5, etc. The AD conversion circuits217, 218 perform analog-to-digital conversion for the input signal thatis input from the receiving circuit 223. More specifically, the ADconversion circuit 217 converts the I-signal into a digital I-signal andthe AD conversion circuit 218 converts the Q-signal into a digitalQ-signal. It should be noted that quadrature demodulation may not beperformed and only a single-channel signal may be received. In thiscase, only one AD conversion circuit has to be provided. When aplurality of antennas are provided, AD conversion circuits in the numbercorresponding to the number of the antennas may be provided. Thereception processing circuit 214 corresponds to the section thatperforms the processing following the AD conversion out of theprocessing of the receivers 22 and 122 as illustrated in FIGS. 4 and 5,etc. Specifically, the reception processing circuit 214 performsdemodulation processing for the signal that has been subjected to theanalog-to-digital conversion, processing of removing the preamble andthe PHY header, and the like processing, and delivers the frame that hasbeen processed to the control circuit 212.

It should be noted that a switch may be arranged in the RF unit forswitching the antennas 50(1) to 50(N) between the transmitting circuit222 and the receiving circuit 223. By controlling the switch, theantennas 50(1) to 50(N) may be connected to the transmitting circuit 222at the time of transmission and the antennas 50(1) to 50(N) may beconnected to the receiving circuit 223 at the time of reception.

Although the DA conversion circuits 215, 216 and the AD conversioncircuits 217, 218 are arranged on the side of the baseband unit 211 inFIG. 17, another configuration may be adopted where they are arranged onthe side of the RF unit 221.

It should be noted that the wireless communicator may be formed by thetransmitting circuit 222 and the receiving circuit 223. The wirelesscommunicator may be formed by further adding DA conversion circuits 215,216 and the DA conversion circuits 217, 218 to the transmitting circuit222 and the receiving circuit 223. The wireless communicator may beformed by including, in addition to these components, the PHY processingportions (i.e., the modulator and the demodulator) of the transmissionprocessing circuit 213 and the reception processing circuit 214.Alternatively, the wireless communicator may be formed by the PHYreception processing portions of the transmission processing circuit 213and the reception processing circuit 214.

Eighth Embodiment

FIG. 18(A) and FIG. 18(B) are perspective views of a wirelesscommunication terminal (wireless device) in accordance with an eighthembodiment. The wireless device of FIG. 18(A) is a laptop PC 301 and thewireless device of FIG. 19(B) is a mobile terminal 321. They correspond,respectively, to one form of the terminal (which may operate as eitherthe base station or the slave station). The laptop PC 301 and the mobileterminal 321 incorporate the wireless communication devices 305, 315,respectively. The wireless communication devices that are previouslydescribed may be used as the wireless communication devices 305, 315.The wireless device incorporating the wireless communication device isnot limited to the laptop PC or the mobile terminal. For example, thewireless communication device may be incorporated in a television,digital camera, wearable device, tablet, smartphone, etc.

In addition, the wireless communication device can be incorporated in amemory card. FIG. 19 illustrates an example where the wirelesscommunication device is incorporated in the memory card. The memory card331 includes a wireless communication device 355 and a memory card body332. The memory card 331 uses the wireless communication device 335 forwireless communications with external devices. It should be noted thatthe illustration of the other elements in the memory card 331 (e.g.,memory, etc.) is omitted in FIG. 19.

Ninth Embodiment

A ninth embodiment includes a bus, a processor, and an externalinterface in addition to the configuration of the wireless communicationdevice in accordance with any one of the first to eighth embodiments.The processor and the external interface are connected via the bus tothe buffer. The firmware runs on the processor. In this manner, byproviding a configuration where the firmware is included in the wirelesscommunication device, it is made possible to readily modify thefunctionality of the wireless communication device by re-writing of thefirmware.

Tenth Embodiment

A tenth embodiment includes a clock generator in addition to theconfiguration of the wireless communication device in accordance withany one of the first to eighth embodiments. The clock generator isconfigured to generate a clock and output the clock on the outputterminal and to the outside of the wireless communication device. Inthis manner, by outputting the clock generated within the wirelesscommunication device to the outside thereof and causing the host side tooperate based on the clock output to the outside, it is made possible tocause the host side and the wireless communication device side tooperate in a synchronized manner.

Eleventh Embodiment

A eleventh embodiment includes a power source, a power sourcecontroller, and a wireless power supply in addition to the configurationof the wireless communication device in accordance with any one of thefirst to eighth embodiments. The power source controller is connected tothe power source and the wireless power supply, and is configured toperform control for selecting the power source from which power issupplied to the wireless communication device. In this manner, byproviding a configuration where the power source is provided in thewireless communication device, it is made possible to achieve low powerconsumption operation accompanied by the power source control.

Twelfth Embodiment

A twelfth embodiment includes a SIM card in addition to theconfiguration of the wireless communication device in accordance withthe eleventh embodiment. The SIM card is connected, for example, to theMAC processor in the wireless communication device or to the controller,etc. In this manner, by providing a configuration where the SIM card isprovided in the wireless communication device, it is made possible toreadily perform the authentication processing.

Thirteenth Embodiment

A thirteenth embodiment includes a video compression/extension unit inaddition to the configuration of the wireless communication device inaccordance with the ninth embodiment. The video compression/extensionunit is connected to a bus. In this manner, by configuring the videocompression/extension unit included in the wireless communicationdevice, it is made possible to readily perform transfer of thecompressed video and the extension of the received compressed video.

Fourteenth Embodiment

A fourteenth embodiment includes an LED unit in addition to theconfiguration of the wireless communication device in accordance withany one of the first to eighth embodiments. The LED unit is connected,for example, to the MAC processor in the wireless communication device,the transmission processing circuit 213, the reception processingcircuit 214, or the control circuit 212, etc. In this manner, byproviding a configuration where the LED unit is provided in the wirelesscommunication device, it is made possible to readily notify theoperating state of the wireless communication device to the user.

Fifteenth Embodiment

A fifteenth embodiment includes a vibrator unit in addition to theconfiguration of the wireless communication device in accordance withany one of the first to eighth embodiments. The vibrator unit isconnected, for example, to the MAC processor in the wirelesscommunication device, the transmission processing circuit 213, thereception processing circuit 214, or the control circuit 212, etc. Inthis manner, by providing a configuration in which the vibrator unit isprovided in the wireless communication device, it is made possible toreadily notify the operating state of the wireless communication deviceto the user.

Sixteenth Embodiment

FIG. 20 illustrates an overall configuration of a wireless communicationsystem in accordance with a sixteenth embodiment. This wirelesscommunication system is an example of the body area network. Thewireless communication system includes a plurality of nodes includingnodes 401, 402 and a hub 451. Each node and the hub are attached to thehuman body, and each node performs wireless communication with the hub451. Being attached to the human body may refer to any case where it isarranged at a position near the human body such as a form in which it isin direct contact with the human body; a form in which it is attachedthereto with clothes existing in between; a form in which it is providedon a strap hanging from the neck; and a form in which it is accommodatedin a pocket. The hub 451 is, by way of example, a terminal including asmartphone, mobile phone, tablet, laptop PC, etc.

The node 401 includes a biological sensor 411 and a wirelesscommunication device 412. As the biological sensor 411, for example,sensors may be used that are adapted to sense body temperature, bloodpressure, pulse, electrocardiogram, heartbeat, blood oxygen level,urinal sugar, blood sugar, etc. Meanwhile, sensors adapted to sensebiological data other than these may be used. The wireless communicationdevice 412 is any one of the wireless communication devices of theembodiments that are described in the foregoing. The wirelesscommunication device 412 performs wireless communication with thewireless communication device 453 of the hub 451. The wirelesscommunication device 412 performs wireless transmission of thebiological data (sensing information) sensed by the biological sensor411 to the wireless communication device 453 of the hub 451. The node401 may be configured as a device in the form of a tag.

The node 402 includes a biological sensor 421 and a wirelesscommunication device 422. The biological sensor 421 and the wirelesscommunication device 422, the explanations of which are omitted, areconfigured in the same or similar manner as the biological sensor 411and the wireless communication device 412 of the node 401, respectively.

The hub 451 includes a communication device 452 and a wirelesscommunication device 453. The wireless communication device 453 performswireless communications with the wireless communication device of eachnode. The wireless communication device 453 may be the wirelesscommunication device described in the context of the previousembodiments or may be another wireless communication device other thanthose described in the foregoing as long as it is capable ofcommunications with the wireless communication device of the node. Thecommunication device 452 is wire or wireless-connected to the network471. The network 471 may be the Internet or a network such as a wirelessLAN, or may be a hybrid network constructed by a wired network and awireless network. The communication device 452 transmits the datacollected by the wireless communication device 453 from the individualnodes to devices on the network 471. The delivery of data from thewireless communication device 453 to the communication devices may beperformed via a CPU, a memory, an auxiliary storage device, etc. Thedevices on the network 471 may, specifically, be a server device thatstores data, a server device that performs data analysis, or any otherserver device. The hub 451 may also incorporate a biological sensor inthe same or similar manner as the nodes 401 and 402. In this case, thehub 451 also transmits the data obtained by the biological sensor to thedevices on the network 471 via the communication device 452. Aninterface may be provided in the hub 451 for insertion of a memory cardsuch as an SD card and the like and the data obtained by the biologicalsensor or obtained from each node may be stored in the memory card. Inaddition, the hub 451 may incorporate a user inputter configured toinput various instructions by the user and a display for image displayof the data, etc.

FIG. 21 is a block diagram illustrating a hardware configuration of thenode 401 or node 402 illustrated in FIG. 20. The CPU 512, the memory513, the auxiliary storage device 516, the wireless communication device514, and the biological sensor 515 are connected to a bus 511. Here, theindividual components 512 to 516 are connected to one single bus, but aplurality of buses may be provided by a chipset and the individual units512 to 516 may be connected in a distributed manner to the plurality ofbuses. The wireless communication device 514 corresponds to the wirelesscommunication devices 412, 422 of FIG. 20, and the biological sensor 515corresponds to the biological sensor 411, 421 of FIG. 20. The CPU 512controls the wireless communication device 514 and the biological sensor515. The auxiliary storage device 516 is a device that permanentlystores data such as an SSD, a hard disk, etc. The auxiliary storagedevice 516 stores a program to be executed by the CPU 512. In addition,the auxiliary storage device 516 may store data obtained by thebiological sensor 515. The CPU 512 reads the program from the auxiliarystorage device 516, develops it in the memory 513, and thus executes it.The memory 513 may be volatile memory such as DRAM, etc., or may benon-volatile memory such as MRAM, etc. The CPU 512 drives the biologicalsensor 515, stores data obtained by the biological sensor 515 in thememory 513 or the auxiliary storage device 516, and transmits the datato the hub via the wireless communication device 514. The CPU 512 mayexecute processing associated with communication protocols of layershigher than the MAC layer and processing associated with the applicationlayer.

FIG. 22 is a block diagram that illustrates a hardware configuration ofthe hub 451 illustrated in FIG. 20. A CPU 612, a memory 613, anauxiliary storage device 616, a communication device 614, a wirelesscommunication device 615, an inputter 616 and a display 617 areconnected to a bus 611. Here, the individual units 612 to 617 areconnected to one single bus, but a plurality of buses may be provided bya chipset and the individual units 612 to 617 may be connected in adistributed manner to the plurality of buses. A biological sensor or amemory card interface may further be connected to the bus 611. Theinputter 616 is configured to receive various instruction inputs fromthe user and output signals corresponding to the input instructions tothe CPU 612. The display 617 provides image display of the data, etc. asinstructed by the CPU 612. The communication device 614 and the wirelesscommunication device 615 correspond to the communication device 452 andthe wireless communication device 453 provided in the hub of FIG. 20,respectively. The CPU 612 controls the wireless communication device 615and the communication device 614. The auxiliary storage device 616 is adevice that permanently stores data such as an SSD, a hard disk, etc.The auxiliary storage device 616 stores a program executed by the CPU612 and may store data received from each node. The CPU 612 reads theprogram from the auxiliary storage device 616, develops it in the memory613, and executes it. The memory 613 may be volatile memory such asDRAM, etc., or may be non-volatile memory such as MRAM, etc. The CPU 612stores data received by the wireless communication device 615 from eachnode in the memory 613 or the auxiliary storage device 616, andtransmits the data to the network 471 via the communication device 614.The CPU 612 may execute processing associated with communicationprotocols of layers higher than the MAC layer and processing associatedwith the application layer.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

The invention claimed is:
 1. An electronic apparatus corresponding to ahub communicable with at least one terminal corresponding to a node viaa first channel of a control channel and a second channel of a datachannel, the electronic apparatus comprising: transmission circuitryconfigured to transmit a first beacon frame including “1” in a firstfield indicating a switch of the data channel and including a number ofa third new channel in a second field indicating a channel number viathe second channel informing the at least one terminal that the datachannel will switch from the second channel to the third channel, andtransmit a second beacon frame including the number of the third channelin a third field indicating a data channel number via the first channelafter the data channel is switched from the second channel to the thirdchannel; and reception circuitry configured to receive a data frame viathe third channel after the data channel is switched from the secondchannel to the third channel.
 2. The electronic apparatus according toclaim 1, wherein a beacon interval of the data channel includes a firstperiod used for communication according to an allocated slot, a secondperiod used for communication according to a contention based accessscheme after the first period, and a third period not used forcommunication after the second period, and the reception circuitry isconfigured to receive the data frame via the third channel within thefirst period after the data channel is switched from the second channelto the third channel.
 3. The electronic apparatus according to claim 1,wherein the first beacon frame includes information specifying a beaconframe transmitted at a timing at which the data channel is switched fromthe second channel to the third channel in a fourth field indicative atiming of channel change.
 4. The electronic apparatus according to claim1, wherein the electronic apparatus is attached to a biological body,and forms a body area network with the at least one terminal, and thereception circuitry receives the data frame including sensinginformation acquired by a biosensor from the biological body.
 5. Theelectronic apparatus according to claim 1, further comprising: aprocessor configured to execute firmware; and at least one antenna,wherein the transmission circuitry includes the processor and transmitsthe first beacon frame and the second beacon frame via the at least oneantenna.
 6. The electronic apparatus according to claim 1, furthercomprising: a host processor configured to perform at least a process ofan upper layer than a medium access control (MAC) layer; and a clockgenerator, wherein at least the reception circuitry and the transmissioncircuitry are included in a wireless communication apparatus, a clocksignal generated by the clock generator is supplied to both the hostprocessor and the wireless communication apparatus, and the wirelesscommunication apparatus and the host processor operate according to theclock signal.
 7. The electronic apparatus according to claim 1, furthercomprising at least one of an light emitting diode (LED) and a vibrator,wherein the electronic apparatus notifies a user of an operation stateof the transmission circuitry or the reception circuitry by at least oneof the LED and the vibrator.
 8. A wireless communication methodperformed by an electronic apparatus communicable with at least oneterminal via a first channel of a control channel and a second channelof a data channel, the wireless communication method comprising:transmitting a first beacon frame including “1” in a first fieldindicating a switch of the data channel and including a number of athird new channel in a second field indicating a channel number via thesecond channel informing the at least one terminal that the data channelwill switch from the second channel to the third channel; transmitting asecond beacon frame including the number of the third channel in a thirdfield indicating a data channel number via the first channel after thedata channel is switched from the second channel to the third channel;and receiving a data frame via the third channel after the data channelis switched from the second channel to the third channel.
 9. Thewireless communication method according to claim 8, wherein a beaconinterval of the data channel includes a first period used forcommunication according to an allocated slot, a second period used forcommunication according to a contention based access scheme after thefirst period, and a third period not used for communication after thesecond period, and the wireless communication method further comprisesreceiving the data frame via the third channel within the first periodafter the data channel is switched from the second channel to the thirdchannel.
 10. The wireless communication method according to claim 8,wherein the first beacon frame includes information specifying a beaconframe transmitted at a timing at which the data channel is switched fromthe second channel to the third channel in a fourth field indicative atiming of channel change.
 11. The wireless communication methodaccording to claim 8, wherein the electronic apparatus is attached to abiological body, and forms a body area network with one or moreterminal, and the wireless communication method further comprisesreceiving the data frame including sensing information acquired by abiosensor from the biological body.
 12. The wireless communicationmethod according to claim 8, further comprising: executing firmware in aprocessor; and transmitting the first beacon frame and the second beaconframe via at least one antenna.
 13. The wireless communication methodaccording to claim 8, further comprising: performing at least a processof an upper layer than a medium access control (MAC) layer in a hostprocessor; performing transmission of at least the first beacon frameand the second beacon frame in a wireless communication apparatus;supplying a clock signal generated by a clock generator to both the hostprocessor and the wireless communication apparatus; and operating thewireless communication apparatus and the host processor according to theclock signal.
 14. The wireless communication method according to claim8, further comprising: performing transmission of at least the firstbeacon frame and the second beacon frame in a transmitter; and notifyinga user of an operation state of the transmitter by at least one of anlight emitting diode (LED) and a vibrator.
 15. An electronic apparatuscorresponding to a node communicable with a base station correspondingto a hub via a first channel of a control channel and a second channelof a data channel, the electronic apparatus comprising: receptioncircuitry configured to receive a first beacon frame including “1” in afirst field indicating a switch of the data channel and including anumber of a third new channel in a second field indicating a channelnumber via the second channel informing the electronic apparatus thatthe data channel will switch from the second channel to the thirdchannel, and receive a second beacon frame including the number of thethird channel in a third field of a data channel number via the firstchannel after the data channel is switched from the second channel tothe third channel; and transmission circuitry configured to transmit adata frame via the third channel after the data channel is switched fromthe second channel to the third channel.
 16. The electronic apparatusaccording to claim 15, wherein a beacon interval of the data channelincludes a first period used for communication according to an allocatedslot, a second period used for communication according to a contentionbased access scheme after the first period, and a third period not usedfor communication after the second period, and the transmissioncircuitry is configured to transmit the data frame via the third channelwithin the first period after the data channel is switched from thesecond channel to the third channel.
 17. The electronic apparatusaccording to claim 15, wherein the first beacon frame includesinformation specifying a beacon frame transmitted at a timing at whichthe data channel is switched from the second channel to the thirdchannel in a fourth field indicative a timing of channel change.
 18. Theelectronic apparatus according to claim 15, wherein the electronicapparatus is attached to a biological body, and forms a body areanetwork with the base station, and the transmission circuitry transmitsthe data frame including sensing information acquired by a biosensorfrom the biological body.
 19. The electronic apparatus according toclaim 15, further comprising: a processor configured to executefirmware; and at least one antenna, wherein the reception circuitryincludes the processor and receives the first beacon frame and thesecond beacon frame via the at least one antenna.
 20. The electronicapparatus according to claim 15, further comprising: a host processorconfigured to perform at least a process of an upper layer than a mediumaccess control (MAC) layer; and a clock generator, wherein at least thereception circuitry and the transmission circuitry are included in awireless communication apparatus, a clock signal generated by the clockgenerator is supplied to both the host processor and the wirelesscommunication apparatus, and the wireless communication apparatus andthe host processor operate according to the clock signal.
 21. Theelectronic apparatus according to claim 15, further comprising: at leastone of an light emitting diode (LED) and a vibrator, wherein theelectronic apparatus notifies a user of an operation state of thetransmission circuitry or the reception circuitry by at least one of theLED and the vibrator.
 22. A wireless communication method performed byan electronic apparatus communicable with a base station via a firstchannel of a control channel and a second channel of a data channel, thewireless communication method comprising: receiving a first beacon frameincluding “1” in a first field indicating a switch of the data channeland including a number of a third new channel in a second fieldindicating a channel number via the second channel informing theelectronic apparatus that the data channel will switch from the secondchannel to the third channel; receiving a second beacon frame includingthe number of the third channel in a third field of a data channelnumber via the first channel after the data channel is switched from thesecond channel to the third channel; and transmitting a data frame viathe third channel after the data channel is switched from the secondchannel to the third channel.
 23. The wireless communication methodaccording to claim 22, wherein a beacon interval of the data channelincludes a first period used for communication according to an allocatedslot, a second period used for communication according to a contentionbased access scheme after the first period, and a third period not usedfor communication after the second period, and the wirelesscommunication method further comprises transmitting the data frame viathe third channel within the first period after the data channel isswitched from the second channel to the third channel.
 24. The wirelesscommunication method according to claim 22, wherein the first beaconframe includes information specifying a beacon frame transmitted at atiming at which the data channel is switched from the second channel tothe third channel in a fourth field indicative a timing of channelchange.
 25. The wireless communication method according to claim 22,wherein the electronic apparatus is attached to a biological body, andforms a body area network with the base station, and the wirelesscommunication method further comprises transmitting the data frameincluding sensing information acquired by a biosensor from thebiological body.
 26. The wireless communication method according toclaim 22, further comprising executing firmware in a processor; andreceiving the first beacon frame and the second beacon frame via atleast one antenna.
 27. The wireless communication method according toclaim 22, further comprising: performing at least a process of an upperlayer than a medium access control (MAC) layer in a host processor;performing reception of the first beacon frame and the second beaconframe in a wireless communication apparatus; supplying a clock signalgenerated by a clock generator to both the host processor and thewireless communication apparatus; and operating the wirelesscommunication apparatus and the host processor operate according to theclock signal.
 28. The wireless communication method according to claim22, further comprising: performing reception of at least the firstbeacon frame and the second beacon frame in a receiver; and notifying auser of an operation state of the receiver by at least one of an lightemitting diode (LED) and a vibrator.